Method of making abrasive wheels



Jan. 16, 1940. s B N R HAL 2,187,583

METHOD OF MAKING ABRASIVE WHEELS Filed July 29, 1956 2 Sheets-Sheet 1 j "Z- 5? \j5 Q 27206723 6715: Oral/0 jfiac/fizer Dona/0! Bfi/son Jan. 16, 1940.

O. S. BUCKNER Er AL METHOD OF MAKING ABRASIVE WHEELS Filed July 29, 1936 2 Sheets-Sheet 2 .1720522/0115: Ore/Z 0 5f 2116*726! Dona/o? BIA 1215072 Patented Jan. 16, 1940 UNITED STATES PATENT OFFICE METHOD OF MAKING ABRASIVE WHEELS Application July 29, 1936, Serial No. 93,250

6 Claims.

The present invention relates to a method of making abrasive wheels and is particularly directed to a method for forming an abrasive wheel which, when finished, will be in perfect balance.

Abrasive wheels are commonly made by compressing granular abrasive material, as for example, silicon carbide or crystalline alumina, mixed with a suitable bonding material into the desired wheel shape, preferably in a mold, and

I subsequently curing the bond by the application of heat to harden the wheel. It is essential that abrasive wheels, which are to be driven at high speeds, be in perfect dynamic and static balance in order that any vibration of the wheels may be eliminated, especially where the abrasive wheel is used for fine grinding or polishing and an outof-balance wheel would produce unevenness or chatter marks in the work being ground.

In order to obtain wheels which are homogeneous in character and in good balance the material must be evenly distributed throughout the mold and then compressed to aunilorm mass before curing the wheel. Several attempts have been made to obtain a uniform distribution of the abrasive material in the mold, but these attempts have not, however, produced an entirely uniform wheel, with the result that the wheel must be balanced after curing. This balancing is generally done by inserting small plugs of lead on the light side of the wheel near the central opening, and the hole which must be made in the wheel to receive the lead frequently weakens the wheel with the result that the wheel may later to pieces, in operation, as a result of the centrifugal force developed by the rapid rotation of the wheel. The present invention avoids the necessity for these lead inserts by balancing the wheel before curing.

Although the abrasive material, after being packed in the mold, is greatly compressed under extremely high pressures to obtain a solid wheel, the abrasive material is of such a consistency that it does not flow laterally during the compression and non-uniformity in the distribution of the abrasive material in the mold is thus not corrected during the compression of the abrasive material. One of the principal objects of the present invention is to provide for the formation of an abrasive wheel which, when finished, will be uniform in character and which will be in static balance without the necessity for balancing the wheel after the wheel is compressed and cured.

1 According to the present invention the abrasive material is distributed in the mold in such a manner that the material, before being compressed or cured, is in perfect static balance on a point coinciding with the axis about which the wheel, when finished, will be rotated. By so balancing the material before curing, the material is easily distributed to obtain perfect balance and the finished wheel will be in perfect static balance. The necessity for subsequent balancing of the wheel is entirely eliminated. Furthermore, in the manufacturing of wheels by this method, the number of wheels that must be discarded for being nonuniform is greatly decreased, or entirely eliminated, and the wheels produced are much safer since they are entirely homogeneous.

Other and further objects and advantages of the invention will more fully appear from the following detailed description taken in connec tion with the accompanying drawings in which:

Fig. 1 is a front elevation of an apparatus by which the method of the present invention may be carried out.

Fig. 2 is a plan View, with parts in section, of the apparatus of Fig. 1.

Fig. 3 is a sectional view on an enlarged scale 85 of the suspending mechanism for the balancing table. Fig. 4 is a fragmentary sectional view of a leveling plate used in uniformly distributing the abrasive material in the mold.

Like reference characters refer to like parts in the different figures.

With reference first to Fig. l, the apparatus by which the method is preferably carried out embodies a base I mounted on any suitable support 2, which may be in the form of a table, which will bring the device at the right height for the workman. The base has upwardly extending parallel posts 3 at opposite ends thereof and the upper ends of the posts are connected by a cross bar 4, securely held on the posts 3 as by nuts 4'. Centrally of the cross bar is provided an opening 5 through which a supporting member 6 extends, this member being substantially in the form of a hook. A key 1 holds the mem her 6 against turning movement in the cross bar and a hand wheel 8 engages the threaded upwardly projecting shank 9 of the supporting member 6 for raising or lowering said member relative to the cross bar.

Projecting upwardly from the base are a plurality of uniformly spaced leveling screws H] which are threaded into the base, each screw having a clamping nut II to provide for locking of said screws against turning, after adjustment 9'! of the screws for raising or lowering a balancing plate l2 resting on the upper ends thereof. The plate 12 has secured to the underside thereof a supporting member i3 from which project horizontally a plurality of threaded rods M on which are mounted internally threaded weights l5 preferably having their outer surfaces knurled to provide for turning thereof on the rods M.

The balancing plate 52 is hung from the hook 6 by a wire it having a connector H at its upper end engaging over the flat portion l8 of the supporting member 6. A connector I9 at the lower end of the wire has an annular groove 20, Fig. 3, engageable by a U-shaped plate ill. The lower end of the member it rests on the plate 2! and is supported thereby. Thus, when the hand wheel 8 is turned to raise the balancing plate 12 from the leveling screws 19, the plate is suspended by the wire I6.

On the top of the plate is positioned a sleeve 22 engaging over the connector it which extends through a bore 23 centrally of the plate l2 and member I3. The sleeve 22 locates the mold plate 24 centrally of the balancing plate, and an annular shell 25, forming a part of the mold, is positioned around the plate 24. The shell 25 is preferably held slightly above the balancing plate 52 by blocks 26, the purpose of which will hereinafter appear.

To obtain suspension of the balancing plate about a single point, the flat portion of the member 6 has a screw 27 having its upper end cupshaped to receive a ball 28. The yoke 29 forming a part of the connector H, and positioned over the portion 18, also has a screw 36, having its lower end cup-shaped to engage the ball 28. The connector H also has tapered jaws 3!, Fig. l, threaded to engage in a bore 32 in the yoke 29, and the upper end of the wire it is clamped between said jaws. The lower connector IQ for the wire comprises a tube'body 33 adapted to fit in the central bore 23 in the member 13. A threaded cap 34 on the upper end of the body 33 holds in place split jaws 35 fitting in a tapered recess 36 in the body. The wire it is located centrally of the body and thus centrally of the balancing plate by these jaws which form the pivotal support for the balancing plate and associated parts. The lower end of the body 33 receives a threaded stud 31 having a bore 38 therethrough for the wire l6. Clamping jaws 39 are threaded into a collar 4!] and securely clamp the lower end of the wire is, the collar 40 having an arcuate end il engageable with the correspondingly shaped head of the stud 3?. The head of the stud also engages the washer 2] to hold the tube body 33 in place.

Adjustment of the stud 37 in the tube body raises or lowers the position of the split jaws 35 relative to the balancing plate and mold parts so that the point where the wire i6 projects from the jaws may be adjusted close to the center of gravity of the mold parts as desired. It will be understood that the sensitiveness of the apparatus is controlled by the position of the pivotal support for the parts being balanced, and the point of support is accordingly adjusted until desired accuracy is obtained.

In use, the hand wheel 8 is turned to raise the balancing plate I2 from its support on the screws l0, and said plate, with the mold parts 22, 24 and 25 and blocks 26 thereon, is brought into perfect balance by adjustment of the weights l5. When the plate is in balance it is indicated by a circular spirit 1evel'42, of Well known construction,

mounted on the plate and indicating any out-ofbalance condition. The mold parts 22, 24 and 25, and the plate I2 have preferably been previously balanced individually so that there will be, at the most only a slight out-of-balance to correct.

When the balancing plate l2 with the mold parts thereon is in perfect balance, the abrasive material A is placed in the mold and uniformly distributed therein until the plate and material are again in perfect balance. This uniform distribution may be in part aided by a gage which, as shown in Fig. 4, comprises a cross bar 43, to which is secured a plate 44, having a straight lower edge 45. The cross bar rests on the upper edges of the sleeve 22 and shell 25 and is revolved around the suspending wire to level the abrasive material in the mold. The plate may be made adjustable on the cross bar if desired. It will .be apparent that the gage distributes the abrasive material so that the cross section of the annulus of abrasive material is uniform throughout, and when the mold and material are in balance it will indicate a uniform density of abrasive material throughout the mold.

If the abrasive material, when leveled within the mold, is not in perfect balance, a slight amount more of the material is added to the light side of the wheel until the material is in perfect balance. In the making of thick wheels, it is frequently desirable to balance the abrasive material at more than one time, as, for example, when one-half the material is in the mold, and again when all the material is in the mold.

Afterthe abrasive material is reduced to a uniform cross section throughout the mold and is in perfect balance, the mold, with the material therein, is removed from the device, by removing the washer 2i and withdrawing the connector Hi from the sleeve 22. A plate similar to the plate 24 is placed on top of the abrasive material and the entire mold compressed to pack the material. The subsequent steps of curing the material and testing the wheel are performed in the usual manner.

From the-foregoing it will be apparent that the invention involves the method of forming a uniform grinding wheel which includes the step of balancing the abrasive material before curing, at which time it is possible to obtain a uniform distribution of material, by weight, about the axis on which the wheel, when completed, is to be rotated.

We claim,

1. fhe method of making an abrasive wheel which comprises balancing the wheel mold on a point coinciding with the axis of the wheel to be molded, distributing the abrasive material in the mold so that the material and mold are again in balance about the same point, and subsequently compressing the abrasive mate-rial to form a wheel having the desired dimensions.

2. The method of making an abrasive wheel which comprises balancing the wheel mold on a point coinciding with the axis of the wheel to be molded, distributing a part of the abrasive material in the mold so that the material and mold are again in balance about the same point, subsequently distributing the remainder of the material in the mold with the material of a uniform depth throughout and with the mold and material again in balance about the same point, and subsequently compressing the abrasive material.

3. In the method of making an abrasive wheel, the steps which comprise determining the quantity of abrasive material required for the Wheel,

distributing a part of the abrasive material in a mold in such manner that the material has a uniform cross-section in any plane passing through the axis of the wheel to be molded, and

with the material in balance about a point 00- inciding with the axis of the wheel to be molded, subsequently distributing the remainder of the material in the mold with the material having a uniform cross-section in any plane including the axis of the wheel to be molded, and with the material in the mold again in balance about the same point and subsequently compressing the abrasive material to form a wheel having the desired dimensions. Y

4. In the method of making an abrasive wheel, the steps which comprise distributing the wheel material in a mold without substantial compressing thereof so that the material has a uniform cross-section in all planes passing through the axis of the wheel being molded and with the material in balance about an axis coinciding with the axis of the wheel being molded and subsequently compressing the material in the mold to the desired wheel dimension.

5. In the method of making an abrasive wheel, the steps which comprise distributing the wheel material in a mold in substantially uncompressed condition in such a manner that the material is in balance about an axis coinciding with the axis of the wheel being molded and has a uniform cross-section in all planes passing through the axis of the wheel being molded, and subsequently compressing the material to a cross-sectional area substantially that of the finished wheel.

6. In the method of making an abrasive wheel, the steps which comprise distributing the Wheel material in a mold in substantially uncompressed condition in such a manner that the material is in balance about an axis coinciding with the axis of the wheel being molded and has a uniform cross-section in all planes passing through the axis of the wheel being molded, compressing the material to a cross-sectional area substantially that of the finished wheel, and then curing the wheel material.

ORELLO S. BUCKNER. DONALD B. WILSON. 

